The “Your site may be linked to SMS fraud” in Yandex.Webmaster if the site uses methods that allow debiting money from the user's mobile account without their knowledge. For example, such a site may offer an SMS subscription to a service. However, information about the subscription price isn't provided explicitly or isn't available at all.
For more information about SMS fraud, see Yandex.Browser Help.
If you already fixed the violations, wait for the automatic recheck. If it doesn't detect any misleading content, a warning in Yandex.Browser will be removed automatically within a month. If after a month the site still opens with a warning, it is likely that the violations were not completely eliminated. In this case, make sure that all the violations are cleared and wait for a recheck.